The proposed project is an investigation of a potentially valuable animal model for the study of specific anosmia to androstenone, a steroid derivative of testosterone. Specific anosmia to androstenone occurs in approximately 40% of human adults tested, and age and sex differences in sensitivity have been reported. Investigation of responses to androstenone in the pig is of particular interest because previous work has indicated that androstenone plays a role in chemical communication in swine and that pigs' behavioral responses to the steroid vary with age and sex. Specific questions to be addressed by the study are whether the lack of behavioral response to androstenone in certain groups of pigs reflects an inability to detect the chemical, analogous to specific anosmia in humans, and if the developmental shift in sensitivity to androstenone during adolescence noted in humans also occurs in swine. Pigs' ability to detect androstenone will be determined using a discrete trials, "go, no-go" successive discrimination task. The animals will be trained to discriminate between an odor and a blank, opening a reward box in the presence of one, but not in the presence of the other. In order to investigate effects of age and sex on detection of androstenone, the study will include 6 groups of 8 pigs: mature females, intact and castrated mature males, prepubertal females, and intact and castrated prepubertal males. Measuring and comparing the ability of pigs of different ages and sexes to detect androstenone will indicate whether the sensitivity shift in humans and the dimorphic behavioral responses in swine are analogous, and whether further study of the pigs' psychophysical responses to the steroid can increase understanding of specific anosmia in particular, and of coding in olfaction in general.